The present invention relates to a visual inspection apparatus for inspecting variations in the thickness of an object to be inspected, such as a semiconductor wafer, inconsistencies which have occurred during the working of minute patterns, or variations between production lots.
Macroscopic inspection as to the presence or absence of variations in the thickness of a semiconductor wafer, inconsistencies which have occurred during the working of a minute pattern, and variations between production lots of the semiconductor wafers has been generally performed such that a semiconductor wafer is observed under a dark field by obliquely radiating intensive light onto the semiconductor wafer or that a semiconductor wafer is observed with regular reflection using a large-scale plane illumination. In this inspection, an operator observes variations in colors while inclining the semiconductor wafer in various directions to detect inconsistencies which have occurred during the working of the semiconductor wafer. To detect variations between production lots of the semiconductor wafers, the operator must depend on his own memory.
Direct visual inspection of a wafer to be performed by an operator poses difficulty in maintaining cleanliness or involves occurrence of contamination because an operator need to approach the wafer. Thus, direct visual inspection presents an obstacle in improving quality of a wafer. Further, inspection of a wafer which requires an operator to incline a wafer in various directions imposes a load on an operator. For these reasons, automatic inspection of a wafer has been desired.
A conceivable method for automating inspection of a wafer is to observe images captured by a CCD camera or the like using a mechanism for inclining a wafer in the same manner as does an operator. Such a mechanism involves a complicated construction. In a case where the images of a wafer are captured while the wafer is inclined greatly, the resultant images become distorted or defocused.
In the case of checking variations in respective production lots of wafers on the basis of an operator""s memory, the inconsistencies is difficult to be recognized.
The present invention has been conceived in light of the drawbacks of the background art and is aimed at providing a visual inspection apparatus capable of readily and correctly inspecting inconsistencies which have arisen during the working of an object to be processed or variations between respective production lots of the objects.
The present invention provides the followings:
(1) A visual inspection apparatus for visual inspection of an object, the apparatus comprising:
image input means for inputting a plurality of monochrome images obtained from at least one object;
image preparing means for preparing a plurality of computed color images based on the monochrome images thus inputted;
a color display; and
display control means for switchingly displaying the computed color images on the color display.
(2) The apparatus of (1), wherein the display control means switchingly displays the computed color images at predetermined time intervals.
(3) The apparatus of (1), wherein the display control mans swtichingly displays the computed color images in a predetermined order.
(4) The apparatus of (1), further comprising:
illumination means for illuminating the object with an illumination light;
wavelength selection means for selecting a narrow band light having a desired center wavelength from the illumination light or a reflected light from the object illuminated with the illumination light, the wavelength selection means capable of variably setting the desired center wavelength;
capturing means for capturing an image of the object using the narrow band light thus selected;
wherein the image input means inputs the monochrome images captured by the capturing means using the narrow band lights having different center wavelengths.
(5) The apparatus of (4), wherein the wavelength selection means variably sets the desired center wavelength to be an arbitrary value falling within 450 nm to 800 nm.
(6) The apparatus of (1), wherein the image preparing means divides the inputted monochrome images into sets each having three monochrome images, and presumes the three monochrome images of each set as red, green and blue images, respectively, to prepare an associated one of the computed color images.
(7) The apparatus of (6), wherein:
the image input means inputs the monochrome images obtained using lights of different wavelengths; and
the image preparing means divides the monochrome images into the sets based on the wavelengths.
(8) The apparatus of (7), wherein:
the image input means inputs the monochrome images obtained using different narrow band lights having respective center wavelengths falling within a range of 450 nm to 800 nm; and
the image preparing means divides the monochrome images into the sets based on the centered wavelengths of the lights used to obtain the monochrome images.
(9) The apparatus of (8), wherein the display control means switchingly displays the computed color images on the display in an order determined based on the centered wavelengths of the lights used to obtain the monochrome images, the order being at least one of an order from a shorter wavelength to a longer wavelength and an order from a longer wavelength to a shorter wavelength.
(10) The apparatus of (6), wherein:
the image input means inputs the monochrome images obtained from the plural objects manufactured by different production lots; and
the image preparing means divides the monochrome images into the sets based on time-sequence of the manufacture by the production lots.
(11) The apparatus of (10), wherein the display control means switchingly displays the computed color images on the display in an order determined based on the time-sequence of the manufacture by the production lots, the order being at least one of an order from an earlier manufacture to a later manufacture and an order from a later manufacture to an earlier manufacture.
(12) The apparatus of (6), wherein the image input means inputs, as the monochrome image, at least four monochrome images.
(13) A visual inspection apparatus for visual inspection of an object, the apparatus comprising:
an image processor which stores a processing program and prepares a plurality of computed color images based on a plurality of inputted monochrome images in accordance with the processing program;
a color display; and
a display controller which stores a displaying program and controls the display to switchingly display the computed color images in accordance with the displaying program.
(14) The apparatus of (13), further comprising an image pick-up element which obtains a monochrome image of the object and inputs the obtained monochrome image to the image processor.
(15) The apparatus of (14), further comprising an illumination unit which illuminates the object with an illumination light.
(16) The apparatus of (13), wherein the processing program includes:
first step of dividing the inputted monochrome images into sets each having three monochrome images; and
second step of presuming the three monochrome images of each set as red, green and blue images, respectively.
(17) The apparatus of (13), wherein the processing program includes:
first step of dividing the inputted monochrome images into sets each having three monochrome images based on each of wavelengths which are used for obtaining the inputted monochrome images; and
second step of presuming the three monochrome images of each set as red, green and blue images, respectively.
(18) The apparatus of (17), wherein the displaying program includes the step of displaying the computed color images in an order determined based on the wavelength.
(19) The apparatus of (13), wherein the processing program includes:
first step of dividing the inputted monochrome images into sets each having three monochrome images based on each of production lots of plural objects which are used for obtaining the inputted monochrome images; and
second step of presuming the three monochrome images of each set as red, green and blue images, respectively.
(20) The apparatus of (19), wherein the displaying program includes the step of displaying the computed color images in an order determined based on the production lots.
(21) The apparatus of (13), wherein the displaying program includes the step of displaying the computed color images at predetermined time intervals and in a predetermined order.
(22) The apparatus of (13), wherein the image processor prepares at least two computed color images based on at least four inputted monochrome images.
The present disclosure relates to the subject matter contained in Japanese patent application No. Hei. 11-340241 (filed on Nov. 30, 1999), which is expressly incorporated herein by reference in its entirety.